1. Field of the Invention
The present invention relates to wireless communications and, more particularly, to a method and apparatus for transmitting a downlink control signal in a wireless communication system.
2. Related Art
As machine type communication (MTC) or machine to machine (M2M) communication is recently introduced, a variety of scenarios are required. The M2M communication is one type of data communication including one or more entities that do not require an interaction with people. That is, the M2M communication refers to a concept in which a machine device not a mobile station (MS) used by people performs communication using a network, such as an existing GSM/EDGE radio access network (GERAN), a universal mobile telecommunications system (UMTS), or 3rd generation partnership project (3GPP) long-term evolution (LTE). Pieces of information can be exchanged without the intervention of people between subscriber stations or a subscriber station and a server through the M2M communication. A machine device used in the M2M communication can be called an MTC device or an M2M device, and the M2M device is various like a vending machine and a machine for measuring the water level of a dam. That is, the M2M communication can be widely applied to various fields. Cellular M2M applications applicable to the M2M communication can include secured access surveillance, health care, smart grid, tracking/tracing recovery, remote maintenance control, automotives, public safety, mobile payment, and consumer electronics.
The MTC can mean many M2M devices coupled through autonomously integrated communication techniques and systems and having various types of quality of service (QoS). The M2M device has different features from a common MS, and service optimized for M2M can be different from service optimized for human type communication (HTC). Cellular M2M requirements can include 1) low power consumption for an M2M device having a limited battery, 2) the support of many M2M devices within a cell, 3) high reliability within a cellular environment, 4) a time-controlled operation, 5) a wider range for mobility for various cellular M2M applications, and 6) the efficient support of the transmission of a small burst, as compared with current mobile network communication service.
As M2M communication is introduced, a base station (BS) needs to support connection between many M2M devices and scheduling for the transmission of a small amount of data. To this end, a BS needs to transmit a downlink control signal to many M2M devices, which can result in overload for a downlink control channel. Accordingly, there is a need for an efficient method of assigning a downlink control channel for an M2M device.